Thermoplastic sheets are well known for use in the field of radiation therapy treatment, including Intensity Modulated Radiation Therapy (IMRT). Typically, such thermoplastic sheets are heated and then formed to a shape corresponding to the body part to be restrained, such as a mask for restraining a patient's head. The sheet is mounted on a frame which can be secured to a treatment table to facilitate proper positioning of the patient on the table for radiation treatment.
The prior art thermoplastic sheets are solid sheets or perforated sheets. Solid thermoplastic sheets require much higher forces to form, retain much more heat and tend to have excess shrinkage when formed to the body shape, all of which leads to patient discomfort. The perforations serve to reduce the force necessary to form, minimize the heat transferred to the patient, and minimize shrinkage of the thermoplastic material. When the sheet is formed into a facemask, the holes permit a patient to see and breathe through the sheet, and thereby minimize or eliminate claustrophobic feelings. The holes can be punched into the sheet, or formed when the sheet is made in an injection molding process. However, totally perforated sheets do not offer the necessary rigidity which is present in a solid or non-perforated sheet.
Accordingly, a primary objective of the present invention is the provision of an improved thermoplastic sheet for use in medical procedures, including IMRT.
Another objective of the present invention is the provision of an improved thermoplastic sheet having perforations and non-perforated reinforcing bands.
Further objective of the present invention is the provision of an improved perforated thermoplastic sheet with enhanced rigidity.
Another objective of the present invention is the provision of an improved thermoplastic sheet which is sufficiently rigid, and which avoids excess shrinkage.
A further objective of the present invention is the provision of an improved thermoplastic sheet, which is comfortable when used on a patient for medical procedures.
These and other objectives will become apparent from the following invention.